Extensible drill

ABSTRACT

An extensible drill assembly comprising a plurality of separate drill members having different drill diameters which are arranged to permit assembly of two or more of the drill members into a continuous drill combination having a stepwise increasing diameter from the outermost drill member.

The present invention relates to a novel type of drill, particularly foruse in the sheet metal and manufacturing industry, which is of the kindthat permits drilling of several aperture dimensions with the samedrilling unit.

Certain drilling operations, such as, for example, the drilling of sheetmetal panels, such as radio and TV chassis, instrument panels and thelike, usually requires holes of various dimensions to be drilled in thesame plate. To avoid changing drills for each hole dimension,cone-shaped drill bodies have been proposed which comprise a series ofcylindrical sections having a stepwise increasing diameter from thenarrow end of the drill body. With such a drill holes having diameterscorresponding to the dimensions of the stepwise arranged drill sectionsof the drill body may be drilled by simply successively drilling astep-by-step larger hole until the desired hole size has been achieved.Drills of this type are, for example, described in the U.S. Pat. Nos.2,897,696, 3,564,945 and 3,758,222.

These drills have, however, several limitations and disadvantages. Thus,only thin materials, such as thin sheet metal and the like, can bedrilled, since the drill body will be unreasonably long if each sectionis made longer and it in addition shall contain a sufficient number ofdiameters.

Further, when cutting a larger hole it is necessary to drill through theworkpiece with all the underlying drill diameters of the drill, whichwill be more time-consuming than to conventionally prebore with asmaller drill and then change to a wider drill corresponding to thedesired hole dimension. Moreover, the drill body will essentially beunusable, if any of the drill sections is damaged.

According to the invention there is suggested a drill utilizing theadvantages of the above described combination drill, i.e. that severalhole dimensions can be bored without any exchange of drills, but whichlacks the mentioned disadvantages and limitations. This is achieved witha drill of extensible type, comprising a plurality of separate drillmembers of mutually different drill diameters, which can be put togetherin any desired combination into a continuous drill body of two or moreof the drill members having a stepwise increasing diameter from theoutermost drill member. When a number of holes of varying dimensions areto be drilled in, for example, a sheet metal panel, the drill memberscorresponding to the desired hole sizes are selected and assembled intoa continuous drill body, which is then mounted in the drilling machine,generally by means of a mounting adapter in the form of a chuck shaft orthe like. A drill is thus provided which is particularly adapted toprecisely the hole dimensions to be drilled and consequently contains nounnecessary drill sections. As a result thereof the length of each drillsection can be made considerably greater than in the previously knownfixed combination drill according to the above U.S. patents without thetotal drill body becoming unreasonably long for a moderate number ofhole sizes. This means in turn that it is possible to drill considerablythicker materials, so that the combinable drill of the invention to asubstantial extent can replace conventional fixed drills. Further, onemay proceed directly from a small hole to a larger hole without havingto drill through the workpiece with all the intermediate drilldimensions as with the fixed combination drill. If any one of the drillmembers should be damaged, it will only be necessary to replace thatvery member, while a fixed combination drill as above must be consideredas substantially unusable when any one of the drill sections has beendamaged.

The attachment of the drill members to each other can be made in variousways, but a suitable embodiment is to make the drill members screwableon to each other by screwing of a central thread tap of a drill memberinto a corresponding threaded axial central recess of the adjacent drillmember. Preferably, the thread taps are arranged on the top part of thedrill members. To render a simple assembly and disassembly of the drillmembers possible, each drill member is provided with suitable means forthe application of a tool, such as a wrench grip.

Optionally one or more drill members of cutter type may be included inthe drill set for plane countersinking for washer seats or the like.Suitably the last drill of the drill ladder may be such a cutter member.

The above described extensible drill of the invention has great utilitywithin the sheet metal and manufacturing industry, where verytime-consuming work can be saved. The inventive concept is, of course,also applicable to other areas and to drilling in other materials.Further, the expression "drill member" is also to be considered ascomprising comparable cutter tools and the like.

In the following an example of an embodiment of the invention will bedescribed in connection with the accompanying drawings, wherein

FIG. 1 is a perspective view of a set of separate, combinable drillmembers of the invention,

FIG. 2 is a side-elevation of a drill consisting of a combination ofdrill members of FIG. 1,

FIG. 3 is a side-elevation of another combination of drill members ofFIG. 1, and

FIG. 4 is a schematical side-elevation, partially transparent, of stillanother combination of drill members corresponding to FIG. 1 and adaptedfor mounting in a drill chuck.

FIG. 1 shows six drill members designated by the letters A-F havingstepwise increasing drill diameters in said order. Each drill member A-Fcomprises a cutting portion with cutting edges 1 and a mounting portionin the form of a central thread tap 2 projecting from the upper part ofthe cutting portion. In their lower part the drill members are providedwith a threaded axial central recess 3 arranged to receive the threadtap 2 of another drill member. The lower part of the drill members areterminated by a plane end portion 4. The cutting portion of the drillmembers are terminated by a corresponding plane surface 5, from whichthe thread tap 2 protrudes. In FIG. 1 the drill member A, or theso-called starting drill, comprises two cutting sections 6 and 7 havingdifferent diameters. The drill member A may, of course, also be made astwo separate drill members, as is shown in FIG. 4 (A₁, A₂). The numberof cutting edges on the drill members naturally vary with theirdiameters, and it may be suitable to have two cutting edges on thethinner drill members and three to four on the thicker ones. In theFIG., for example, the drill members A-C are illustrated as having twocutting edges, while the drill members D-F have three cutting edges. Ofcourse, both the shape and number of the cutting edges may be varied. Asbest appears from FIGS. 2-4, the drill members A-F are further providedwith wrench grip 8 in the upper part of the cutting portion tofacilitate the assembly and disassembly, respectively, of the drillmembers, as will be described in more detail below.

The drill members A-F in FIG. 1 may be combined with each other inarbitrary manner, the starting drill A, however, always being used asthe outermost drill member. Two drill members A-F are assembled byscrewing the thread tap 2 of one drill member into the threaded recess 3of the succeeding drill member in the desired combination. The threadedrecess 3 is somewhat deeper than the length of the thread tap, so thatwhen two drill members have been screwed together the lower end face 4of one drill member contacts the upper end face 5 of the other. In FIGS.2-4 examples of various combinations of drill members A-F in FIG. 1 areshown. Thus, in FIG. 2 the drill members A, B and D are combined, whilethe drill body of FIG. 3 comprises the drill members A, D och F. In FIG.4, finally, the drill members A₁, A₂ (corresponding to A in FIG. 1), B,E and F are included. In FIG. 4, as mentioned above, the starting drillconsists of two separate drill sections A₁ and A₂, which make itpossible to change the dimension of the proper starting drill A₁. Due tothe thin dimension of the drill member A₁ its thread tap 2a₁ mustusually be made narrow. The other thread taps 2, as well as the recesses3, otherwise have the same dimension to render the combinableness of theinvention possible. The wrench grips 8, which suitably may consist oftwo opposed chamfered portions in the upper part of the drill members,facilitate the assembly and in particular, the disassembly of the drillmembers.

The extensible drill of the invention may be used in hand drillingmachines as well as column and radial drilling machines. To fix thedesired combination of drill members A-F in the drilling machine inquestion, a drill or chuck fastener 9, which in one end thereof isprovided with a threaded, axial recess 10, is screwed onto the top drillmember, i.e. the one having the largest dimension. The shape of thedrill or chuck fastener 9 is adapted to the fastening device or chuck ofthe drill machine and may, for example, for fixing in a column drillingmachine be tapered. The length of the drill or chuck fastener is alsodetermined by the hole depth to be drilled, i.e. the thickness of theworkpiece to be drilled. Suitably drill or chuck fasteners 9 of varyinglength are provided in the drill set.

Optionally one or more drill members designed as drill steels or cuttermeans for plane countersinking, e.g. for washer seats, may be includedin a drill set according to the invention. Suitably, the last drillmember, i.e. of the largest diameter, in a drill ladder A-F may bedesigned for such plane countersinking.

The dimensions of the drill members in the extensible drill ladder ofthe invention may be varied to suit various needs. For various workswithin the sheet metal and manufacturing industry, for example, astarting drill of about 4-10 mm (depending on whether a hand drillingmachine or a fixed drilling machine is to be used) may be suitable, theother drill members having a stepwise increasing diameter of up to about80-100 mm.

When, for example, a hole of a large diameter is to be drilled in aplate or a beam, say with a dimension corresponding to the drill memberE of FIG. 1, the starting drill A and the drill member E are screwedtogether, the chuck fastener 9 is fixed to the drill member E and thechuck fastener is fixed in the drilling machine chuck. The hole is thenbored with the starting drill A (which is done in two steps with thedrill sections 6 and 7) and the drilling is then directly continued withthe drill E. To drill a corresponding hole in conventional manner it isnecessary to first prebore with a smaller drill and then change to thedrill having the larger drill dimension. When it, for example, is aquestion of wider drills than about 15 mm, it may be necessary to alsoexchange the chuck therebetween. Through the extensible drill of theinvention this timeconsuming procedure is thus completely obviated andthe drilling can be carried out in one single moment. When several holesizes are to be bored in one and the same plate, the saving of time bynot having to exchange chucks and drills will be even greater. In such acase the drill members in the drill ladder A-F giving the desired holedimensions are selected and screwed together into a continous drill bithaving a step-by-step increasing drill diameter, e.g. the combination A,D, F according to FIG. 3. After that the chuck fastener 9 is screwed onto the drill member F as above and the whole unit is fixed in thedrilling machine. Each hole is then gradually bored to the desired sizeby successive through-boring with the drill members A, D, F until thedesired hole size has been achieved. When necessary, the whole drillladder may be assembled, which in the shown case permits seven differenthole diameters.

The drill sets for the extensible drill according to the invention may,of course, contain more than the six drill members A-F according toFIG. 1. Further, the length of each drill member may be varied dependingon the material thickness to be worked. The number of drill members thatmay be included in a drill ladder will then, of course, becorrespondingly restricted, as such a drill ladder otherwise wouldbecome too long. Also, other drill members than the starting drill A maycomprise a fixed combination of cutting sections having differentdiameters, although in such a case the flexibility of that extensibledrill will be reduced correspondingly.

The invention is, of course, not restricted to the above specificallyshown and described embodiments, but many variations and modificationsmay be made within the scope of the general inventive concept, as statedin the subsequent claims. This especially concerns the design of thecuts of the drill members as well as the design of the coupling meansfor assembly the various drill members.

I claim:
 1. An extensible drill assembly for drilling holes of differentdiameters with the same assembly comprising:(a) a front drill member;(b) a plurality of rear drill members having different drill diameters;(c) the front drill member including at least one cutting portionextending peripherally and axially thereof and means for detachablyconnecting the front drill member to one or more rear drill members; (d)each rear drill member including first means for detachably connectingone end thereof to either the front drill member or another rear drillmember and second means for detachably connecting the other end thereofto either a drilling machine or another rear drill member, whereby thefirst and second detachable connection means permit the rear drillmembers to be connected to each other in any desired number andcombination; and (e) the connected drill members being of stepwiseincreasing diameters from the front drill member to the last rear drillmember.
 2. The drill assembly of claim 1 wherein:(a) the means forconnecting the front drill member to one or more rear drill membersincludes a threaded tap; (b) the first detachable connection means ofeach rear drill member includes a threaded recess; and (c) the seconddetachable connection means of each rear drill member includes athreaded tap.
 3. The drill assembly of claim 1 wherein the front drillmember includes two cutting portions of different diameters.
 4. Thedrill assembly of claim 1 wherein the front drill member and each reardrill member are provided with means engageable by a tool for connectingthe drill members together.
 5. The drill assembly of claim 1 wherein therear drill member having the largest drill diameter is configured forplane countersinking.
 6. The drill assembly of claim 1 wherein the frontand rear drill members each include two to four cutting edges.
 7. Thedrill assembly of claim 1 further including at least one chuck fastenerfor detachable connection to the second detachable connection means ofany of the rear drill members.
 8. The drill assembly of claim 7 furtherincluding plural chuck fasteners of different lengths.